ICE said the unit worked on information they developed about a suspected drug smuggling attempt near Ventana, AZ, one of the villages on the Nation’s property. The Shadow Wolves officers tracked two vehicles that left tire tracks travelling through the desert near the village, said ICE. Officers found a Chevrolet pickup truck hidden in some brush and concealed behind a camouflage tarp. The truck, said ICE, contained more than 1,900 pounds of marijuana, wrapped in 84 individual bales. A short time later, officers located the second vehicle -- a Chevrolet SUV -- that contained more than 1,800 pounds of marijuana, also broken down into 84 bales. ICE estimated the seized marijuana has an estimated street value of nearly $1.9 million.

Both seizures were made with significant assistance from the Tohono O'odham Police Department, according to the agency.

The "Shadow Wolves" is a unit of Native American trackers created in 1972 to track smugglers through a 76-mile stretch of wilderness in the Tohono O'odham Nation territory that runs along the Mexico/Arizona border. The Tohono O’odham Nation sprawls across more than 2 million square acres of rugged, remote terrain and specialized tracking skills are required in the wilderness. The Shadow Wolves units eschew most modern technological tracking, instead relying on traditional methods of locating suspected smugglers, including observing minute physical evidence on the trail, like torn clothing threads, broken twigs and traces of footprints.

"The Shadow Wolves are well known for not giving up when they've caught the scent of a smuggling attempt, said Rodney Irby, assistant special agent in charge of ICE HSI in Sells. "In this case, they were able to work closely with the Tohono O'odham police to make this significant seizure.

No arrests have yet been made in this ongoing investigation, said ICE.